1. Field of the Invention:
The present invention relates to a library apparatus including a storage cabinet defining cells and a grasping mechanism designed to move relative to the storage cabinet to access the individual cells. In particular, the invention relates to a method and an apparatus for detecting an inclination, preferably utilized to correct the attitude of the grasping mechanism in the library apparatus. The invention also relates to a method and an apparatus for controlling the position of an object, preferably utilized to correct the position of the grasping mechanism.
2. Description of the Prior Art:
A grasping unit is often utilized for transporting a magnetic tape cartridge in a magnetic tape library apparatus. The grasping unit is designed to move along a horizontal plane in the rectangular coordinates based on first and second rails perpendicular to each other. Likewise, the grasping unit is designed to move in the vertical direction based on the vertical movement of the first and second rails. The grasping unit can be positioned at a target cell through the horizontal and vertical movement. The attitude of the grasping unit is for example changed around the vertical axis to get opposed to a storage cabinet including the target cell prior to the vertical and horizontal movement. The grasping mechanism in this manner serves to insert and withdraw a magnetic tape cartridge into and from the target cell.
A positional error occurs between the storage cabinet and the first and second rails as well as between the storage cabinet and the grasping unit when the grasping unit is assembled in the magnetic tape library apparatus. Such a positional error hinders the accurate positioning of the grasping unit. As disclosed in Japanese Patent Application Publication 2004-93265, a CCD, charge-coupled device, sensor on the grasping unit may be utilized for measurement of the positional error, for example. The CCD sensor is designed to capture an image of a sign fixed on the storage cabinet. The position of the grasping unit can be compensated in the horizontal and/or vertical directions based on the captured image.
The attitude of the grasping unit can be changed around the vertical axis, for example. If the attitude of the grasping unit deviates from the standard attitude around the vertical axis, for example, the grasping unit cannot insert or withdraw a magnetic tape cartridge into or from the target cell even though the grasping unit is positioned right at the target cell.